Technical Field
The present invention relates to a radiographic apparatus that emits radiation to a subject to take a fluoroscopic image. More particularly, the present invention is directed to a radiographic apparatus that allows plural-time imaging successively.
Background Art
A medical institution is equipped with a radiographic apparatus that emits radiation to image a subject M. See, for example, Patent Literature 1. Such a radiographic apparatus includes a radiation source 53 emitting radiation, and an FPD 54 detecting radiation, as illustrated in FIG. 13. The subject M stands between the radiation source 53 and the FPD 54.
The radiographic apparatus has a field of view determined from a size of the FPD 54. Consequently, in order to image the subject over an area larger than the size of the FPD 54, plural-time imaging is required while the FPD 54 is moved relative to the subject, as illustrated in FIGS. 14(A), 14(B), and 14(C). When the imaging is performed while the FPD 54 is moved as noted above, an imaging position varies correspondingly. The images obtained at this time contain various FIGs of sites of the subject. Then, combining the images allows an image with a large field of view. Such an imaging method is referred to as long-length radiography.
The plural-time imaging in the long-length radiography should be performed rapidly. That is because a longer time period between the adjacent imaging causes movement of the subject during the imaging, leading to a deviation of FIGs at a joint of the images. Such a method for successive imaging has been devised conventionally.
Examples of conventional imaging method include a method of performing imaging one by one manually. If an operator presses down a startup switch of the radiation source 53, the radiation source 53 in a rest state activates. Then, if the operator presses down an emission-startup switch, the radiation source 53 emits X-rays, and the FPD 54 detects X-rays passing though the subject M. Radiographing a first image is completed in this manner. After the radiography, the radiation source 53 is brought back into a rest state. Thereafter, the FPD 54 is in a standby state until next radiography is ready for performance. Here, no radiography is performable when the FPD 54 is in the standby state. Consequently, a standby period time is provided while the FPD 54 is restored from the standby state.
After the standby period time, if the operator presses down the startup switch of the radiation source 53 again, the radiation source 53 in the rest state activates again for the next radiography. With the radiographic method, in order to take three images, the operator should press down the switch for starting preparation of the radiation source 53 three times, and press down the switch for X-ray emission three times. Such a radiographic method is referred to as a manual mode.
The manual mode mentioned above requires many-time press of the switch by the operator. Accordingly, another imaging mode that allows simple operation of the operator has been devised by adding some ideas to the method mentioned above. In the other imaging method, when the operator presses down the startup switch of the radiation source 53, the radiation source 53 activates and is not changed into the rest state until the radiography completes. Then, if the operator presses down the switch to start emission, X-rays are automatically emitted at given time intervals successively. Here, a time period between anterior and posterior X-ray emission is set longer than that required for restoring the FPD 54 from the standby state. In the radiographic method, the operator is only required to press down the switch one time for preparing the radiation source 53, and one time for X-ray emission even for taking three images. Such an imaging method is referred to as an automatic mode.